Purchase orders always use the tax rate set against the Supplier of the purchase order for the item - even if this Supplier isn’t the primary supplier of the item.
Transfers (both In and Out) always use the tax rate of the Item itself.
Purchase Orders
In the screenshots below, we can see the Tax Rate of the item is Zero Rated:
However, the Supplier Tax of this item is 20%:
When the item is placed on a Purchase Order, the Tax Rate is set at 20%, as this is the supplier tax rate:
Transfers
In the case of Transfers, using the same example item, we can see that the tax rate of the item itself - Zero Rated - is used:
At the Goods Out stage:
And at Goods In:
